High‐Efficiency Spin–Orbit Torque Switching Using a Single Heavy‐Metal Alloy with Opposite Spin Hall Angles

Abstract Spin–orbit torque (SOT) induced perpendicular magnetization switching in Pt 1‐x Gd x /Co/Al 2 O 3 heterostructure with x = 0, 0.02, 0.14, 0.30, and 0.33 is investigated. With in‐plane charge current flowing through the Pt 1‐x Gd x layer, field‐free current‐induced magnetization switching is observed for all nonzero x due to the existence of opposite spin Hall angles (θ SHA ) from Pt 1‐x Gd x alloys. Furthermore, the large θ SHA of about 0.27 is obtained in the optimal Pt 0.70 Gd 0.30 alloy films, which is about four times larger than that of the pure Pt. This work suggests a simple and scalable method for realizing field‐free SOT switching, and provides potential candidates of spin Hall materials that can be used to produce highly efficient SOTs.